Badminton preferentially decreases explosive over maximal voluntary torque in both the plantar flexors and extensors

We assessed changes in maximal and explosive plantar flexion (PF) and dorsi flexion (DF) torque, and thus the maximal and explosive DF/PF ratio, in response to succes- sive badminton matches (2 × 35, 15 minutes of rest) in 16 juniors (10 males, 6 fe- males) International-level badminton players before (Pre), immediately after the first (Post- 1) and second (Post-2) match as well as after resting for 12 hours. For both PF and DF, maximal voluntary torque decreased from Pre to Post-2 (~7%-9%; P < 0.05). Compared with Pre, PF explosive voluntary torque decreased by ~4%-13% at Post-1 (P < 0.05), with further reductions ranging from −15% to −25% within the 0-100 ms epoch after contraction (P < 0.001) at Post-2. Decrements of similar magnitude in DF explosive voluntary torque occurred at Post-1 (ranging −7% to −27%) and Post-2 (ranging −3% to −28%) relative to Pre (P < 0.05). All neuromuscular parameters were fully recovered after 12 hours of rest. Explosive DF/PF ratios during the very initial phase of contraction (up to 50 ms from onset) were lower compared with the maximal DF/PF ratio, with no effect of time (all P < 0.05). In badminton, explosive torque indices should be included to more accurately reflect acute fatigue induced by successive badminton matches.SIFunding received from Badminton World Federation (BWF)

Sex differences in muscle morphology of the knee flexors and knee extensors

Introduction Females experience higher risk of anterior cruciate ligament (ACL) injuries; males experience higher risk of hamstring strain injuries. Differences in injury may be partially due to sex differences in knee flexor (KF) to knee extensor (KE) muscle size ratio and the proportional size of constituent muscles. Purpose To compare the absolute and proportional size, and mass distribution, of individual KE and KF muscles, as well as overall size and balance (size ratio) of these muscle groups between the sexes. Methods T1-weighted axial plane MR images (1.5T) of healthy untrained young males and females (32 vs 34) were acquired to determine thigh muscle anatomical cross-sectional area(ACSA). Maximal ACSA (ACSAmax) ofconstituent muscles, summated for KF and KE muscle groups, and the KF:KE ratio were calculated. Results Females had 25.3% smaller KE ACSAmax (70.9±12.1 vs 93.6±10.3 cm2; P<0.001) and 29.6% smaller KF ACSAmax than males (38.8±7.3cm2 vs 55.1±7.3cm2; P<0.001).Consequently, females had lower KF:KE ACSA ratio (P = 0.031). There were sex differences in the proportional size of 2/4 KE and 5/6 KF. In females, vastus lateralis (VL), biceps femoris long-head (BFlh) and semimembranosus (SM) were a greater proportion and sartorius(SA), gracilis (GR) and biceps femoris short-head (BFsh) a smaller proportion of their respective muscle groups compared to males (All P<0.05). Conclusion Sex differences in KF:KE ACSAmax ratio may contribute to increased risk of ACL injury in females. Sex discrepancies in absolute and proportional size of SA, GR, VL and BFlh may contribute further anatomical explanations for sex differences in injury incidence

The dose-response of the nordic hamstring exercise on biceps femoris architecture and eccentric knee flexor strength : A randomized interventional trial

Purpose: To examine the dose–response of the Nordic hamstring exercise (NHE) on biceps femoris long head (BFlh) architecture and eccentric knee flexor strength. Design: Randomized interventional trial. Methods: Forty recreationally active males completed a 6-week NHE training program consisting of either intermittent low volumes (group 1; n = 10), low volumes (group 2; n = 10), initial high volumes followed by low volumes (group 3; n = 10), or progressively increasing volumes (group 4; n = 10). A 4-week detraining period followed each program. Muscle architecture was assessed weekly during training and after 2 and 4 weeks of detraining. Eccentric knee flexor strength was assessed preintervention and postintervention and after 2 and 4 weeks of detraining. Results: Following 6 weeks of training, BFlh fascicle length (FL) increased in group 3 (mean difference = 0.83 cm, d = 0.45, P = .027, +7%) and group 4 (mean difference = 1.48 cm, d = 0.94, P = .004, +14%). FL returned to baseline following detraining in groups 3 and 4. Strength increased in group 2 (mean difference = 53.6 N, d = 0.55, P = .002, +14%), group 3 (mean difference = 63.4 N, d = 0.72, P = .027, +17%), and group 4 (mean difference = 74.7, d = 0.83, P = .006, +19%) following training. Strength returned to baseline following detraining in groups 2 and 3 but not in group 4. Conclusions: Initial high volumes of the NHE followed by lower volumes, as well as progressively increasing volumes, can elicit increases in BFlh FL and eccentric knee flexor strength. Low volumes of the NHE were insufficient to increase FL, although as few as 48 repetitions in 6 weeks did increase strength

Implementing hamstring injury prevention programmes remotely: a randomised proof of concept trial

Objectives This study aimed to (1) compare the effectiveness of a Nordic hamstring exercise (NHE) versus single-leg Romanian deadlift (SLRDL) exercise programme on a hamstring injury risk surrogate; (2) compare the muscle soreness experienced by both exercise programmes; and (3) assess compliance to remote injury prevention exercise protocols through video software.Methods Twenty participants (10 women and 10 men: 21.45±1.6 years; 176±23 cm; 70±10 kg) were randomised into an NHE or SLRDL programme for 6 weeks. Single-leg hamstring bridge (SLHB), a hamstring injury surrogate, was the primary outcome for exercise efficacy. Muscle soreness and exercise adherence were also assessed. Significance was set at p&lt;0.05.Results Both exercises increased SLHB performance resulting in an overall effect (p=0.013) with no effect for group (p=0.470) and no interaction effect (p=0.709), indicating both groups improved but there was no difference in improvement between interventions. There was no difference in muscle soreness between groups (p=0.087). Finally, both groups had 100% adherence to the programme.Conclusions Both the NHE and SLRDL are equally effective in increasing SLHB performance and demonstrate a similar level of muscle soreness. This suggests that SLRDL may be a viable option as a preventative exercise to mitigate the risk of hamstring injury. Finally, implementing injury prevention programmes remotely has the potential to enhance adherence

Example of MRI slice mid-thigh with the knee extensors and flexors manually segmented.

<p>Example of MRI slice mid-thigh with the knee extensors and flexors manually segmented.</p

Proportional size of individual muscles relative to whole muscle group size (ACSAmax %knee extensor (A) %knee flexor (B) ACSAmax).

<p>Data are mean±SD of males (n = 32) and females (n = 34). * P<0.05.</p

The magnitude of the sex difference for individual KE (dark grey) and KF (light grey) muscles.

<p>Data are presented as mean female ACSAmax (n = 34) as the percentage less than mean male ACSAmax (n = 32). The sex difference ranged from 16.1% for the VL to 43.6% for the SA.</p

Knee flexors (KF) to knee extensor (KE) ACSAmax ratio for individual participants (diamonds) and mean for males (n = 32, dark grey bar) and females (n = 34 light grey bar).

<p>* P<0.05.</p